But since it is a component it can have a direction, too, so can go up l between negative l and positive l.

但因为它是个分量,它是有方向的，所以它可以,从负的l一直到正的。

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Once you do that, I think it's fairly clear that it has got a y component that's given by cosine the x component is negative.

用了这个结论,我想很明显,y 分量由 cos φ 给出,它的 x 分量是负的

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